Gear pumps have been employed in a variety of industries and environments. In general, gear pumps include a housing with one or more plates that hold a set of intermeshing gears. As the gears turn, fluid moves between the gear teeth and the housing and is discharged from the pump due to the intermeshing of the gears. The gears are attached to shafts that run axially from the gear faces, and these shafts run on one or more bearing surfaces.
Lubrication of bearing surfaces in gear pumps is often provided by the fluid being conveyed through the pump. One problem with such an arrangement is that upon startup, an adequate lubricating film may not be present (or may not be immediately generated) and thus some bearing surfaces can be subject to wear resulting in damage or premature failure. For example, where an inadequate lubricating film exists between the side faces of the gears and the adjacent end plates, wear related damage to the gears and/or end plates can occur. This problem has previously been addressed by employing hydrodynamic slide bearings with variable depth, and/or through the use of gall-resistant materials aimed at withstanding harsh contact. Surface treatments or coatings of other wear resistant materials have also been applied to the plate surface to resist galling.
Problems with these approaches include difficulty in generating adequate thrust (using the aforementioned slide bearings) without adversely affecting the pumps overall efficiency. In addition, under adverse pumping conditions, gall-resistant materials are still subject to premature failure.
Thus, there is a need for an improved design for reducing wear in gear pumps, particularly in gear and endplate bearing surfaces.